Non-shorting winding connection for tap changer on series-multiple transformer

ABSTRACT

A tap changer winding connection for a series-multiple transformer. One of the windings is provided with a plurality of continuous turns equal to the multiple or parallel voltage of the transformer. The winding is also provided with a plurality of tap connections. A second winding portion, discontinuous from the first winding is also provided having a plurality of tap connections. One or more other windings are provided also having sufficient continuous turns equal to the multiple or parallel voltage of the transformer. A series-multiple switch is provided for connecting the windings in series or in parallel. When connected in parallel, the winding having the tap connections is connected in parallel with all of the continuous turns equal to the parallel voltage connected, thus effectively disconnecting the tap changer from the parallel connected windings.

United States Patent Conway [541 NON-SHORTING WINDING CONNECTION FOR TAPCHANGER ON SERIES-MULTIPLE TRANSFORMER [72] Inventor: Gerard V. Conway,Pittsfield, Mass.

[73] Assignee: General Electric Company [22] Filed: Dec. 10, 1971 [21]Appl. No.: 206,726

[ 51 Sept. 12, 1972 Primary Examiner-Thomas J. Kozma Attorney-Francis X.Doyle et a1.

[5 7] ABSTRACT A tap changer winding connection for a series-multipletransformer. One of the windings is provided with a plurality ofcontinuous turns equal to the multiple or parallel voltage of thetransformer. The winding is also provided with a plurality of tapconnections. A second winding portion, discontinuous from the firstwinding is also provided having a plurality of tap connections. One ormore other windings are provided also having sufficient continuous turnsequal to the multiple or parallel voltage of the transformer. Aseriesmultip1e switch is provided for connecting the windings in seriesor in parallel. When connected in parallel, the winding having the tapconnections is connected in parallel with all of the continuous turnsequal to the parallel voltage connected, thus effectively disconnectingthe tap changer from the parallel connected windings.

4 Claims, 8 Drawing Figures PATENTEDSEP 12 m2 SHEET 1 OF 2 fmfwfir, 56mmV ['om/ NON-SHORTING WINDING CONNECTION FOR TAP CHANGER ONSERIES-MULTIPLE TRANSFORMER BACKGROUND OF THE INVENTION This inventionrelates to series-multiple transformers and more particularly to anon-shorting winding connection for use with tap changers inseries-multiple transformers.

As is well known to those skilled in the transformer art, it is commonpractice to provide transformers which have a dual voltage rating. Ingeneral, the term dual voltage rating is applied to transformers whichare provided with a low voltage setting and a high voltage setting forthe high voltage winding. It may be that more than two different voltageratings are provided such as, for example, a plurality of high voltageratings and a single low voltage rating. However, the transformers aredesignated as dual voltage rating transformers and it will be understoodthat the term dual voltage rated transformer or similar phrases usedthroughout the specification and claims will relate to transformerswhich are provided with a high voltage rating and a low voltage ratingalthough there may be more than one high voltage rating for suchtransformers. In general, the dual voltage of the dual voltage ratedtransformer is provided by means of a multiple primary winding which maybe connected in either series or in parallel to provide thedesiredvoltage ratings for the transformer. For example, a transformermay be provided with a plurality of 2,400 volt windings. When thesewindings are connected in parallel, the voltage rating of thetransformer will be 2,400 volts. However, when the windings areconnected in series, the transformer will have a voltage ratingaccording to the number of 2,400 volt windings which are provided in thetransformer. For example, when three windings are provided, the voltagerating would be 7,200 volts. As

- will be apparent by use of a series-parallel switch,

which is generally referred to in the art as a series-multiple switchand will be so designated throughout the specification and claims, therating of the transformer can be changed from either the low voltage orthe high voltage rating, as desired.

In many instances, utilities have required that their dual voltagetransformers be provided with a variable series high voltage rating. inother words, many utilities require that their dual voltage ratedtransformers be provided with a high voltage series rating which mayvary over a specified range. For example, one such transformer may havea low voltage multiple rating of 2,400 volts and be provided with a highvoltage series rating of, for example, 8,000 volts, 7,810 volts or someother similar rating. Utilities require the plurality of high voltageseries ratings because in many instances utilities have different areaswhere different high voltage rating requirements are found. In order tominimize the various types of transformers which utilities are requiredto stock, they generally require that a single transformer be availablewhich will be useful for any of their high voltage rating requirements.

In order to provide the desired dual voltage rating transformers with aplurality of high voltage series ratings, it is necessary that either aseries-multiple switch having more than two positions be provided, thatis, one that has two separate high voltage series positions, or elsethat a tap changer be provided for use with the high voltage seriesrating. As will be readily understood, a special series-multiple switchprovided with a plurality of high voltage series settings is anecessarily expensive switch. Therefore, in order to limit the cost ofdual voltage rating transformers, it is preferred to utilize a tapchanger to vary the high voltage rating. However, with the use of a tapchanger, a special problem arises that the tap changer may be used whenthe series-multiple switch is in the multiple voltage position. Whenthis occurs in transformers of the prior art, one of the parallelwindings will be at an incorrect voltage rating; this would induce ashort circuit condition in a transformer causing damage and possibledestruction of the transformer. Thus, it is desirable to provide a dualvoltage transformer of low cost having a variable high voltage seriesrating without danger of incorrectly connecting the winding of thetransformer when in the low voltage multiple setting.

This has been done in the prior art by providing an interlocking meansbetween the series-multiple switch and the tap changer such that the tapchanger is placed in the correct position and locked when theseries-multiple switch is placed in the parallel or multiple operatingposition. As will be understood, an interlocking device adds extraexpense to the series-multiple transformer and also adds anothermechanical device which must be maintained during the life of thetransformer. It has long been considered desirable to provide aseries-multiple transformer having a tap changer for the seriesconnection wherein the tap changer is automatically removed from themultiple connection without using mechanical interlocks or the like.

It is, therefore, one object of this invention to provide a relativelylow cost, dual voltage transformer having a variable high voltage seriesrating.

Another object of this invention isto provide a dual voltage transformerin which the variable high voltage series rating is provided by means ofa tap changer.

Yet another object of this invention is to provide a dual voltagetransformer using a tap changer to vary the high voltage series settingof the transformer and in which the tap changer is only operative whenthe series-multiple switch is in its high voltage series operatingposition.

A still further object of this invention is to provide a dual voltagetransformer in which a tap changer is used to vary the high voltageseries rating of the transformer and in which the tap connections areprovided such that in the multiple or parallel operation of thetransformer, the tap changer is out of operative circuit relation withthe tapped winding.

SUMMARY OF THE INVENTION In carrying out this invention in one form, atransformer is provided having a dual voltage rating and having aseries-multiple switch for placing the transformer in either a lowvoltage multiple or a high voltage series mode of operation. A tapchanger is provided such that the high voltage series rating of thetransformer may be varied by varying the position of the tap changer tovary the number of turns in the series connected winding of thetransformer. The tap positions of the windings are so connected thatwhen placed in the multiple or parallel operation the tap changer isremoved from the circuit.

The features of the invention which are believed to be patentable areset forth with particularity in the appended claims. However, it isbelieved that this invention and the manner in which its objects andadvantages are obtained as well as other objects and advantages thereofwill be better understood by reference to the following detaileddescription of a preferred embodiment thereof, especially whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram of one formof the primary windings of a series-multiple transformer according tothis invention;

FIG. 2 is a schematic diagram of the windings of FIG. 1 connected formultiple or parallel operation;

FIG. 2a is a diagrammatic showing of one form of series-multiple switchshowing the switch in the multiple position;

FIG. 3 is a schematic diagram of the winding of FIG. 1 connected forseries operation;

FIG. 3a is a diagrammatic showing of a series-multiple switch in theseries position;

FIG. 4 is a schematic diagram of a slightly different form ofseries-multiple winding using this invention; and

FIGS. 4a and 4b are diagrammatic showing of a series-multiple switch foruse with a winding of FIG. 4 showing the multiple position and theseries position, respectively.

DESCRIPTION OF PREFERRED EMBODIMENT As above noted, this inventionrelates to a seriesmultiple transformer winding provided with tapswherein the taps are provided on one winding such that when the windingsare placed in multiple or parallel operation, the tap changer iseffectively out of the circuit. Reference will now be made to thedrawings for a detailed description of a preferred embodiment of thisinvention. When referring to the drawings, like numerals will be used toindicate like parts throughout the various figures.

Referring first to FIG. 1, there is shown schematically a multiplewinding 10 for use in a series-multiple transformer, not otherwiseshown. As shown, the multiple winding 10 includes a first winding 12having terminals 1 and 2, a second winding 14 having terminals 3, 4, 5and 6 and a third winding 16 having terminals 7 and 8.

For purposes of this description, the series-multiple windings 10 willbe considered as a 2,400 volt by 8,000 volt winding and the windings ashaving 10 volts per turn. Winding 12 is indicated as having 240 turnsbetween terminals 1 and 2 and thus being a 2,400 volt winding betweenthe terminals. Winding 14 is indicated as having 42 turns betweenterminals 5 and 3; 240 turns between terminals 3 and 4; and 38 turnsbetween terminals 6 and 6b. As will be understood, this will provide2,400 volts between terminals 3 and 4. In like manner, winding 16 isindicated as having 240 turns and thus 2,400 volts between terminals 7and 8. When windings l2, l4 and 16 are connected in multiple or parallelas is shown in FIG. 2, there will be three 2,400 volt windings connectedin parallel.

As shown, winding 14 is provided with a tap changer 20 with contact arm22 connectible to taps 4, 4a and 4b, while contact arm 24 is connectibleto taps 6, 6a and 6b. As can be seen, tap 4 on winding 14 is alsoterminal 4 of the winding 14. Therefore, when a connection is made toterminal 4 by the series-multiple switch 30, as shown in FIG. 2a, tapchanger 20 is effectively removed from the circuit regardless of itsposition. As can be seen from FIG. 2, with terminals 1, 3 and 7connected together and terminals 2, 4, and 8 connected together, thewindings 12 and 16 of 2,400 volts each are connected in parallel witheach other and with the portion of winding 14 between terminals 3 and 4which also provides 2,400 volts. As can be seen from FIG. 2, no matterhow tap changer 20 is positioned it will not affect the volts betweenthe terminals 3 and 4. Thus the windings may be placed in paralleloperation without regard to the position of tap changer 20.

FIG. 3 shows the windings l2, l4 and 16 connected in series for highvoltage operation with the tap changer 20 in circuit. FIG. 3a shows theposition of a series-multiple switch 30 to provide the high voltageoperation. As shown, terminal 1 is connected to the high voltagebushing, terminal 2 is connected to terminal 5, terminal 6 is connectedto terminal 7, the tap changer 20 is connected between the tap contacts4 and tap contacts 6, and terminal 8, the other side of winding 10, isconnected to ground. As will be apparent, if all of the turns ofwindings 12, 14 and 16 are in series and there are 10 volts per turnthroughout the winding, the total voltage across the winding 10 will be8,000 volts. However, as shown in FIG. 3, tap changer 20 has contact arm22 on tap 4b and contact arm 24 on tap 6. As can be seen, thiseliminates four sections of winding 14, each section being indicated ashaving 19 turns. Thus, 760 volts have been dropped leaving a totalvoltage across winding 10 of 7,240 volts. Obviously, as tap changer 20is moved to include in each of the sections of winding 14 the voltagewill increase first to 7,430 volts, then 7,620 volts, then 7,810 voltsand, finally, when all sections are in, 8,000 volts across the winding10. From the above, it will be apparent that by means of placing thetaps for the high voltage series setting on portions of the main windingand on additional portions of a second winding wherein one of the tapsis actually one of the terminals, then the connecting of the windings inparallel in the manner shown particularly in FIG. 2, will effectivelyremove the tap changer from the circuit without any need for aninterlock or any need for placing the tap changer on a given set ofcontacts.

FIG. 4 shows a similar winding 10' having three sections, section 32between terminals 1 and 2, section 34 including terminals 3, 5, 4 and 6and section 36 between terminals 7 and 8, wherein the winding 10 may beconnected in either series or multiple. Again considering the winding asbeing one in which there are ten volts per turn then, as can be seen,winding 32 with 240 turns will have a voltage of 2,400 volts betweenterminals 1 and 2. Winding 34 having 240 turns between terminals 3 and 4will also provide 2,400 volts between these terminals and, in a similarmanner, winding 36 having 240 turns will provide 2,400 volts betweenterminals 7 and 8. Thus, when the windings are connected in parallel inthe manner shown by the switch 30 in FIG. 4a with terminals 1, 3 and 7connected together and terminals 2, 4 and 8 connected together, thethree windings are connected in parallel,

each winding having 2,400 volts thereacross. As can be seen in FIG. 4,winding 34 is provided with a tap changer 20 having the arm 22engageable with contacts 4, 4a and 4b while arm 24 is engageable withthe taps 6, 6a and 6b. As is indicated in FIG. 4, between terminals 3and 5 there are 36 turns or, therefore, 360 volts, while between thetaps 4 and 4a, 4a and 4b, 6b and 6a, and 6a and 6, it is indicated asbeing 18 turns and therefore 180 volts between taps. As will beunderstood, since between terminals 3 and 4, there are 240 turns andthus 2,400 volts, then when the windings are connected in parallel inthe manner above discussed, the tap changer 20 is out of circuit.Therefore, there is no need, either to provide an interlock, or to placetap changer 20 in a special position before connecting theseries-multiple switch 30 in multiple, as shown in FIG. 4a.

Winding shown in FIG. 4 is connected in series in the manner shown byswitch 30 in FIG. 4b, that is, terminals 2 to 3 and terminal 6 to 7.Then as will be understood, the total number of turns between terminals1 and terminal 8 of winding 10' is 756 turns. Therefore, the totalvoltage for the series connection may be 7,560 volts between terminals 1and terminal 8. However, in the manner shown in FIG. 4, with contact arm22 on tap 4a and contact arm 24 on tap 6a the sections 4 to 4a and 6a to6b of winding 34 are out of circuit. Therefore, 36 turns have beendropped and thus the voltage across the terminals 1 and 8 will be 7,200volts. Of course, as will be apparent from FIG. 4, by moving the tapchanger the voltage for the series connection may be varied from 6,840volts in steps of 180 volts to 7,020 volts to 7,200 volts to 7,380 voltsand finally to 7,560 volts. Thus the tap changer may be effective, forexample, considering the winding 10 shown in FIG. 4 of a 2,400 volt by7,200 volt transformer, then the connection may be effective to haveplus or minus taps to either increase or decrease the nominal highvoltage of the transformer.

Of course, it will be apparent from FIG. 4, that the series connectionmay be made from terminal 2 to terminal 5 and terminal 6 to 7, providinga different series high voltage. With that series connection, the 36turns between terminals 3 and 5 are necessarily eliminated making themaximum high voltage 7,200 volts. As the tap changer 20 is used toeliminate the various sections of the winding 34, the high voltage willdrop in 180 volt steps from 7,200 volts, to 7,020 volts, 6,840 volts,6,660 volts, and finally to 6,480 volts. Thus, by using differentterminals to connect winding 10 in series, the high voltage may bevaried from the top and the bottom of the range, although the value ofeach step of tap changer 20 remains the same.

Thus, as will be understood, the invention may be utilized in anyseries-multiple transformer of any desired rating and by means ofplacing the taps such that one of the taps is one of the terminals of awinding wherein the winding between the terminals is of the desiredmultiple ratio, then a transformer may be provided having any desiredhigh voltage ratio wherein the multiple ratio will be determined by thevoltage across the windings in parallel.

While there has been shown and described the present preferredembodiment of the invention, it will of cou e be u ders ood that vario uchan es ma be made without eparting from the spirit and s%:ope o theinvention. The invention which is sought to be protected is set forth inthe appended claims.

What is claimed as new and which it is desired to secure by LettersPatent of the United States is:

l. A series-multiple voltage transformer having a series-multiple switchand a tap changer, a plurality of windings connectible in series ormultiple according to the position of said series-multiple switch, oneof said windings including two portions, each of said portions having aplurality of taps, said tap changer being connectible between saidplurality of taps on each of said portions, one of said portions havingat least two terminals, the winding portion between said two terminalshaving a voltage equal to the multiplevoltage of the transformer,whereby when said plurality of windings are connected in multiple, saidtap changer is inoperative.

2. A series-multiple transformer having a series-multiple switch and atap changer, a plurality of windings connectible in series or multipleaccording to the position of said series-multiple switch, one of saidwindings including two portions, each of said portions having aplurality of taps, said tap changer connected between said plurality oftaps on each of said portions, one of said portions having at least twoterminals, one of said terminals being one of said plurality of taps onsaid portion, the winding portion between said two terminals having avoltage equal to the multiple voltage rating of the transformer, placingsaid series-multiple switch in multiple position connecting said windingportion between said two terminals in multiple connection with the otherof said plurality of windings thereby making said tap changerinoperative.

3. A series-multiple voltage transformer having a series-multiple switchand a tap changer, a plurality of windings connectible in series ormultiple according to the position of said series-multiple switch, oneof said windings including two portions, each of said portions having aplurality of taps, said tap changer being connectible between saidplurality of taps on each of said portions, one of said portions havingat least two terminals, the winding portion between said two terminalshaving a voltage equal to the multiple voltage of the transformer, oneof said two terminals being one of said plurality of taps on said oneportion, said other plurality of windings having end terminals with thewinding between said end terminals being equal to the multiple voltageof the transformer, said series-multiple switch in multiple positionconnecting each of said two terminals with one of said end terminals ofeach of said other plurality of windings to place said plurality ofwindings in multiple and remove said tap changer from operation.

4. A series-multiple transformer as set forth in claim 3 in which saidother portion of said one winding has a terminal and in which saidseries-multiple switch in series connects one of said end terminals ofone of said other plurality of windings to one of said two terminals ofsaid one portion and connects one of said end terminals of another ofsaid other plurality of windings to said terminal on said other portionof said one winding, thereby placing said tap changer in operation.

1. A series-multiple voltage transformer having a seriesmultiple switchand a tap changer, a plurality of windings connectible in series ormultiple according to the position of said series-multiple switch, oneof said windings including two portions, each of said portions having aplurality of taps, said tap changer being connectible between saidplurality of taps on each of said portions, one of said portions havingat least two terminals, the winding portion between said two terminalshaving a voltage equal to the multiple voltage of the transformer,whereby when said plurality of windings are connected in multiple, saidtap changer is inoperative.
 2. A series-multiple transformer having aseries-multiple switch and a tap changer, a plurality of windingsconnectible in series or multiple according to the position of saidseries-multiple switch, one of said windings including two portions,each of said portions having a plurality of taps, said tap changerconnected between said plurality oF taps on each of said portions, oneof said portions having at least two terminals, one of said terminalsbeing one of said plurality of taps on said portion, the winding portionbetween said two terminals having a voltage equal to the multiplevoltage rating of the transformer, placing said series-multiple switchin multiple position connecting said winding portion between said twoterminals in multiple connection with the other of said plurality ofwindings thereby making said tap changer inoperative.
 3. Aseries-multiple voltage transformer having a series-multiple switch anda tap changer, a plurality of windings connectible in series or multipleaccording to the position of said series-multiple switch, one of saidwindings including two portions, each of said portions having aplurality of taps, said tap changer being connectible between saidplurality of taps on each of said portions, one of said portions havingat least two terminals, the winding portion between said two terminalshaving a voltage equal to the multiple voltage of the transformer, oneof said two terminals being one of said plurality of taps on said oneportion, said other plurality of windings having end terminals with thewinding between said end terminals being equal to the multiple voltageof the transformer, said series-multiple switch in multiple positionconnecting each of said two terminals with one of said end terminals ofeach of said other plurality of windings to place said plurality ofwindings in multiple and remove said tap changer from operation.
 4. Aseries-multiple transformer as set forth in claim 3 in which said otherportion of said one winding has a terminal and in which saidseries-multiple switch in series connects one of said end terminals ofone of said other plurality of windings to one of said two terminals ofsaid one portion and connects one of said end terminals of another ofsaid other plurality of windings to said terminal on said other portionof said one winding, thereby placing said tap changer in operation.